package com.t7;

/**
 * Created by xuyiwei on 2018/7/18.
 */
class Engine{
    public void start(){};
    public void rev(){};
    public void stop(){};
}

class Wheel{
    public void inflate(int psi){};
}

class Window{
    public void rollup(){};
    public void rolldown(){};
}

class Door{
    public Window window;
    public void open(){};
    public void close(){}
}

public class Car {
    public Engine engine = new Engine();
    public Wheel[] wheels = new Wheel[4];
    public Door
       left = new Door(),
       right = new Door();
    public Car(){
        for(int i=0;i<4;i++){
            wheels[i] = new Wheel();
        }
    }

    public static void main(String[] args) {
        Car car = new Car();
        car.left.window.rolldown();
        car.engine.start();
    }
}
